The present invention generally relates to apparatus for dispensing microliter amounts of medicament and is more particularly directed to apparatus for instilling a medicament into an eye.
A great number of devices have been developed for instilling medicament to an eye. Well know eye drop containers conventionally include a squeezable container and a nozzle for releasing drops of medicament into the eye by compression of the container. Obviously, this apparatus affords no practical method of dispensing a measured dose of medicament inasmuch as the liquid dispensed from the nozzle is dependent upon the amount of compression of the container. Thus, there is no way of accurately controlling the volume of each dose of medicament released into the eye and, further, the smallest drop obtainable is the result of the combined effective gravity and surface tension.
When preservative-free medicaments are utilized, simple eye drop dispensers are not practical because there are no means for preventing the tip from being contaminated due to its exposure to air. Such tip contamination ultimately spreads to the medicament in the container.
In an attempt to overcome these problems, apparatus has been developed for applying a medicament to an eye which includes a nozzle having a seam which is normally in a closed position for preventing the passage of medicament through the nozzle, and which opens in response to a flow of medicament of sufficient pressure to enable opening of the seam in order to permit the passage of medicament through the nozzle for release into the eye, see U.S. Pat. No. 5,685,869.
While this nozzle is suitable, there is difficulty in coupling the nozzle with a suitable reservoir of medicament in order to create a working, producible device for multiple dose delivery of a preservative-free product of sufficient dose accuracy for consumer benefit and regulatory body registration over an extended period of time of up to six months or more.
Operation of prior art devices such as set for the in the hereinabove referenced U.S. Patent typically cause a small negative pressure or vacuum within the medicament container during operation. When a collapsible container is utilized to accommodate shrinking of volume of the medicament reservoir, the materials of construction do not satisfactorily inhibit the permeating of air through the container walls to provide a desired long term use in storage of the device without compromise of the stored medicament.
U.S. patent application Ser. No. 09/435,703 filed Nov. 8, 1999 entitled MULTIPLE PRECISION DOSE PRESERVATIVE FREE MEDICATION DELIVERY SYSTEM provides a nozzle and medicament reservoir combination which enables multiple dose delivery of a preservative-free product with accurate dose dispensing over extended periods of time.
Such axial movement may be provided by a button disposed at a rear of a housing in order to compress a fluid reservoir and actuator together. The compressed condition is held by a latching mechanism and upon release of the latch, or trigger, the two parts are rapidly accelerated apart from each other in an opposite axial direction in the actuator or pump, produces a dose that is sprayed out of a nozzle.
The present invention provides for apparatus enabling axial compression of a spring and the housing for enabling the fluid reservoir to move backward when a trigger is released. The original motion to cock the system is delivered by a patient operated push button or cap at the back of the housing.
An apparatus for instilling a medicament into an eye generally includes a housing having a front and rear with a longitudinal axis therebetween. A reservoir for containing a medicament is provided and disposed in the housing and movable therein therealong the longitudinal axis.
A nozzle disposed proximate the housing front, is provided for instilling a dose of medicament to an eye and an actuator, or pump, disposed between the reservoir and the nozzle is provided for metering doses of medicament from the reservoir to the nozzle and forcing each metered dose through the nozzle upon actuation of the actuator.
A spring is provided for causing a longitudinal displacement of the reservoir toward the housing rear upon release of the spring from a compressed state, the longitudinal displacement causing actuation of the actuator. A depressible button is disposed at the housing rear for moving the reservoir in a forward direction toward the housing front to cause compression or cocking of the spring. A trigger disposed in the housing provide for the release of the compressed spring and causing rearward motion of the reservoir.
More particularly, the trigger may include a latch for holding the spring in the compressed state until depression of the trigger, and preferably the trigger is disposed on a side of the housing.
Importantly, a second spring may be provided and disposed within the housing for causing the depressible button to separate from the reservoir and move towards the housing rear after compression of the spring. This is important in that a comfortable operating position for a patient is often with his or her finger resting on the depressible button.
In order to produce a sufficient consistent dose, which is critical in most of the ophthalmic medication delivery applications, the reservoir must be free to move rearwardly during actuation. If a patient""s finger is resting on the button and the button does not separate from the reservoir, interference with the operation may lead to suboptimal dosing and the risk of patient not receiving sufficient medication. Thus, the second spring enables the button to move independently and decouple, or separate, from the reservoir, thus enabling free movement of the reservoir despite continued contact by a patient with the button.
The present invention further includes apparatus for operating an eye drop dispenser with the eye drop dispenser including a reservoir containing a medicament, a nozzle for instilling a dose of the medicament into an eye and a spring driven actuator for metering doses of medicament from the reservoir to the nozzle and forcing each measured dose through the nozzle upon axial displacement between the actuator and the reservoir along a longitudinal axis. Specifically, this apparatus includes a housing for receiving the reservoir, nozzle and actuator in combination with a depressible button which is disposed at a rear of a housing for moving the reservoir in a forward directional towards a housing front to cause compression of the spring and a trigger disposed in the housing for releasing the compressed spring and causing the rearward motion of the reservoir.